Brittany Kamasinski had heard nothing of the NFL's new security measures when she reached the gates at M&T Bank Stadium on Sunday for a public Ravens practice.

So the Dundalk resident was startled when stadium workers told her she could not enter carrying a baby bag stuffed with diapers, bottles and formula for her 7-month-old daughter.

“Oh well, that's just great!” she thought sarcastically as she and her husband trudged back to their car with the bag. They transferred the baby items to the pockets of his cargo shorts. “You would think they could've posted signs in the parking lot,” Kamasinski said Tuesday. “They have signs for everything else, at least when they're trying to sell you stuff.”

The Ravens expect to encounter such frustrations as fans and stadium workers get used to new, league-mandated security measures that will be in place Thursday night when the team hosts its first preseason game of the 2013 season.

Under the stricter rules, fans will be permitted to carry only clear plastic or vinyl tote bags, gallon-sized clear plastic freezer bags or clutch purses about the size of a person's hand. Larger purses and baby bags will not be allowed.

The Ravens are scrambling to get the word out to ticket buyers. On Tuesday, the team sent an email outlining the changes to its licensed-seat holders. The Ravens also plan to mail clear tote bags bearing the team's logo to customers with season-ticket accounts. The same bags will be for sale on the team's website and at its stores. But those bags won't be in fans' hands by Thursday.

“This is going to be a dramatic change to the way people come into the stadium,” Ravens spokesman Kevin Byrne said. “We're trying to warn people before they come Thursday night.”

Byrne's wife was startled when he told her this week that she wouldn't be able to carry her regular purse to games.

Team officials also promised to surround the stadium with large signs outlining the rules so that fans won't get all the way to the gates with unpermitted bags.

The league announced its new security measures in June, about two months after explosions at the Boston Marathon killed three and injured more than 200. Two brothers allegedly triggered the explosions using pressure-cooker bombs carried in backpacks.

“Certainly, we know that those who seek to do harm will do so where they can get a great deal of exposure,” said Jeff Miller, the NFL's chief security officer.

Miller said the league's committee on stadium security, which includes several team owners, developed the tighter rules in consultation with the FBI and other law enforcement agencies. “I think this is going to be the state of the art,” he said.

The measures might seem overzealous, said Steve Adelman, an Arizona-based attorney who deals with stadium security issues. But the inconvenience is a reasonable trade-off if the policy helps stadium officials catch weapons, alcohol, drugs or, in extreme cases, bombs similar to those used in Boston.

“What I give the NFL a lot of credit for is that you don't wait for disaster before you respond,” Adelman said. “If you give me a little more safety for a little inconvenience, I'll take that deal 10 out of 10 times. There's probably a tipping point somewhere, but I don't think the NFL is anywhere near it.”

At some large college stadiums, all bags are prohibited, while at many sports facilities, including Camden Yards, larger purses, baby bags and small backpacks are still allowed.

The Ravens have long prohibited backpacks and fanny packs from M&T Bank Stadium, and fans have been subject to pat-downs upon entering since 2001.

“We've come up with what we believe is an effective compromise,” Miller said. “We're asking our fans not to bring anything if they don't need to, but if they really need to, to bring it in one of these types of conveyances.”

He predicted that once fans and stadium workers get used to the rules, entry to NFL games will go more quickly because bags will be much easier to check.

The Ravens already plan to offer express lanes for fans who haven't brought any bags. They'll also offer free bag checking along the Ravens Walk between Camden Yards and M&T Bank Stadium and a limited number of plastic freezer bags for fans who need to transfer items. Though the team will distribute its official tote bags to season-ticket holders, officials emphasized that those bags aren't required and that fans are free to bring their own clear bags, no larger than 12 inches by 6 inches by 12 inches.

“These are significant changes to the way people have come into our stadium the last few years,” said Roy Sommerhof, the team's vice president of stadium operations. “But they're all intended to improve safety and efficiency for people coming into our buildings.”

Sommerhof said fans took four or five games to get used to the security pat-downs added in 2001. “It'll take a little time,” he said of the adjustment to this year's new rules.

Other items not allowed in the stadium include coolers, briefcases, seat cushions and camera bags. The ban does not cover handheld items such as cellphones, cameras or blankets; it only prevents them from being carried in nontransparent bags.

Fans who need bags for medical reasons will be able to go to a separate entrance to have them searched.

The new policy won't have an impact on tailgating, as coolers and bags still will be allowed in parking lots.

Efficiency wasn't the word Kamasinski had in mind for her experience Sunday. But she said she understands the reason for the new rules and won't be dissuaded from attending future games.

“I get it,” she said. “After the Boston Marathon, you have to be a little more secure.”

She'll be more prepared the next time. “Now,” she said, “I know I have to make my husband into a diaper bag.”

childs.walker@baltsun.com

New NFL bag rules

What's allowed:

Beginning with preseason games, fans will be able to carry the following style and size of bag, package or container at stadium plaza areas, stadium gates or when approaching queue lines of fans awaiting entry into the stadium:

Bags that are clear plastic, vinyl or PVC and do not exceed 12 inches by 6 inches by 12 inches.

One-gallon clear plastic freezer bag (Ziploc bag or similar).

Small clutch bags, approximately the size of a hand, with or without a handle or strap can be taken into the stadium with one of the clear plastic bags.

What's not allowed:

Prohibited items include, but are not limited to:

Purses larger than a clutch bag

Coolers

Briefcases

Backpacks, fanny packs, cinch bags

Seat cushions, luggage of any kind, computer bags, and camera bags or any bag larger than the permissible size.

Heather Harness, the Ravens' manager of marketing, advertising and game entertainment, demonstrates the types of bags that will be permitted into M&T Bank Stadium under the NFL's new security guidelines.